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Using the Templating Plugin

While you can easily use Genshi templating through the APIs provided directly
by Genshi, in some situations you may want to use Genshi through the template
engine plugin API. Note though that this considerably limits the power and
flexibility of Genshi templates (for example, there's no good way to use filters
such as Genshi's HTMLFormFiller when the plugin
API is sitting between your code and Genshi).

Genshi supports this API out of the box, so you can use it in frameworks like
TurboGears or Pylons without installing any additional packages. A small
example TurboGears application is included in the examples directory of
source distributions of Genshi.

For any given view or controller (or whatever those are called in your
framework of choice), specify the name of the template to use and which data
should be made available to it.

For point 1, you'll have to specify the name of the template engine plugin.
For Genshi, this is "genshi". However, because Genshi supports both markup
and text templates, it also provides two separate plugins, namely
"genshi-markup" and "genshi-text" (the "genshi" name is just an
alias for "genshi-markup").

Usually, you can choose a default template engine, but also use a different
engine on a per-request basis. So to use markup templates in general, but a text
template in a specific controller, you'd configure "genshi" as the default
template engine, and specify "genshi-text" for the controllers that should use
text templates. How exactly this works depends on the framework in use.

When rendering a specific template in a controller (point 3 above), you may also
be able to pass additional options to the plugin. This includes the format
keyword argument, which Genshi will use to override the configured default
serialization method. In combination with specifying the "genshi-text" engine
name as explained above, you would use this to specify the "text" serialization
method when you want to use a text template. Or you'd specify "xml" for the
format when you want to produce an Atom feed or other XML content.

How you specify template paths depends on whether you have a search path set
up or not. The search path is a list of directories that Genshi should load
templates from. Now when you request a template using a relative path such as
mytmpl.html or foo/mytmpl.html, Genshi will look for that file in the
directories on the search path.

For mostly historical reasons, the Genshi template engine plugin uses a
different approach when you haven't configured the template search path:
you now load templates using dotted notation, for example mytmpl or
foo.mytmpl. Note how you've lost the ability to explicitly specify the
file extension: you now have to use .html for markup templates, and
.txt for text templates.

Using the search path is recommended for a number of reasons: First, it's
the native Genshi model and is thus more robust and better supported.
Second, a search path gives you much more flexibility for organizing your
application templates. And as noted above, you aren't forced to use hardcoded
filename extensions for your template files.

The plugin API allows plugins to be configured using a dictionary of strings.
The following is a list of configuration options that Genshi supports. These may
or may not be made available by your framework. TurboGears 1.0, for example,
only passes a fixed set of options to all plugins.

Whether the Python code blocks should be permitted in templates. Specify "yes"
to allow code blocks (which is the default), or "no" otherwise. Please note
that disallowing code blocks in templates does not turn Genshi into a
sandboxable template engine; there are sufficient ways to do harm even using
plain expressions.

Whether the template loader should check the last modification time of template
files, and automatically reload them if they have been changed. Specify "yes"
to enable this reloading (which is the default), or "no" to turn it off.

You probably want to disable reloading in a production environment to improve
performance of both templating loading and the processing of includes. But
remember that you'll then have to manually restart the server process anytime
the templates are updated.

While using the Genshi API directly allows you to specify document
types not in that list, the dictionary-of-strings based
configuration utilized by the plugin API unfortunately limits your
choices to those listed above.

The default behavior is to not do any prepending/replacing of a DOCTYPE, but
rather pass through those defined in the templates (if any). If this option is
set, however, any DOCTYPE declarations in the templates are replaced by the
specified document type.

Note that with (X)HTML, the presence and choice of the DOCTYPE can have a
more or less dramatic impact on how modern browsers render pages that use CSS
style sheets. In particular, browsers may switch to quirks rendering mode for
certain document types, or when the DOCTYPE declaration is missing
completely.

The default output encoding to use when serializing a template. By default,
Genshi uses UTF-8. If you need to, you can choose a different charset by
specifying this option, although that rarely makes sense.

As Genshi is not in control over what HTTP headers are being sent together with
the template output, make sure that you (or the framework you're using)
specify the chosen encoding as part of the outgoing Content-Type header.
For example:

Content-Type: text/html; charset=utf-8

Note

Browsers commonly use ISO-8859-1 by default for text/html, so even
if you use Genshi's default UTF-8 encoding, you'll have to let the
browser know about that explicitly

Serialization to XHTML in a way that should be compatible with HTML (i.e. the
result can be sent using the text/html MIME type, but can also be handled
by XML parsers if you're careful).

html

Serialization to HTML

text

Plain text serialization

See Understanding HTML, XML and XHTML for an excellent description of the
subtle differences between the three different markup serialization options. As
a general recommendation, if you don't have a special requirement to produce
well-formed XML, you should probably use the html option for your web sites.

The callback function that should be invoked whenever the template loader loads
a new template.

Note

Unlike the other options, this option can not be passed as
a string value, but rather must be a reference to the actual function.
That effectively means it can not be set from (non-Python)
configuration files.

The error handling style to use in template expressions. Can be either
lenient (the default) or strict. See the Error Handling section for
detailled information on the differences between these two modes.

The maximum number of templates that the template loader will cache in memory.
The default value is 25. You may want to choose a higher value if your web
site uses a larger number of templates, and you have enough memory to spare.